Analog-to-digital converters (“ADC” or “A/D”) are used in a variety of applications in order to convert a detected analog signal into a digital signal. There are a variety of ADC architectures, such as pipelined, flash, Sigma-Delta, successive approximation register (“SAR”), etc.
For example, a flash ADC uses a linear voltage ladder with a comparator at each “rung” of the ladder to compare the input voltage to successive reference voltages. The reference ladders are constructed of a resistor network, and the outputs from the comparators provide the digital value. Thus, to do an N-bit conversion, a flash ADC requires 2^N comparators, which can result in an ADC that is too big and consumes too much power for some applications.